CASE(F_LTOSVAL);
lvalue_to_svalue_no_free(sp,sp-2);
sp++;
break;
CASE(F_LTOSVAL2);
sp[0]=sp[-1];
lvalue_to_svalue_no_free(sp-1,sp-3);
/* this is so that foo+=bar (and similar things) will be faster, this
* is done by freeing the old reference to foo after it has been pushed
* on the stack. That way foo can have only 1 reference if we are lucky,